THE NONMETALLIC MINERALS. 315 



forms suitable for oriuiincntal work. (See Collection Building- and 

 Ornanionttil Stones.) Color brownish rod, ilosli red, and pink; some- 

 times rose red. Hardness, 5.5 to 0.5. Specific gravity, ;^>.-t to 3.68. 



On exposure the mineral undergoes oxidation, becoming coated 

 with a l)lack film and giving rise thus to indefinite admixtures of silicate, 

 oxides, and carbonates of manganese. 



The mineral occurs in abundance associated with the iron ores of 

 Wermland, Sweden, and at other localities in Europe; in Ekaterin- 

 burg, Russia, as above noted. The zinciferous variety commonly asso- 

 ciated with the zinc ores in granular limestones of Sussex County, New 

 Jersey, is known as fowlerite. (Specimen No. 67405, LJ.S.N.M.) 



So far as the writer has information, rhodonite has as yet little com- 

 mercial value, excepting- as an ornamental stone. To some extent it 

 has been utilized in glazing pottery and as a flux in smelting furnaces. 



12. Steatite; Talc; and Soapstone. 



The mineral steatite, or talc, is a soft micaceous mineral, consisting 

 when pure of 63.5 percent of silica, 31.7 per cent of magnesia, and 4.8 

 per cent of water. Its most striking characteristics are its softness, 

 which is such that it can be readily cut with a knife or even with the 

 thumb nail, and soapy feeling, there being an entire absence of anything 

 like grit. The prevailing colors are white or gray and apple green. 

 Several varietal forms are recognized; the name talc as a rule being 

 applied to the distinctly foliaceous or micaceous variety (Specimen No. 

 72838, U.S.N.M.), while that of steatite is reserved for the compact 

 cryptocrystalline to coarsely granular forms (Specimens Nos. 26137 and 

 63448, U.S.N. M.). 



Pyrallolite and rensselaerite are names given to varied forms of talc 

 resulting from the alteration of hornblende or pyroxene. Such forms 

 are found in various portions of northern New York, Canada, and 

 Finland. 



According to Dana, a part of the so-called agalmatolite used by the 

 Chinese is steatite. 



The name soapstone is given to dark gray and greenish talcose 

 rocks, which are soft enough to be readily cut with a knife, and which 

 have a pronounced soapy or greasy feeling; hence the name. Such 

 rocks are commonly stated in text-books to be compact forms -of stea- 

 tite, or talc, but as the writer has elsewhere pointed out, and as shown 

 by the analyses here given, few of them are even approximately pure 

 forms of this mineral, but all contain varying proportions of chlorite, 

 mica, and tremolite, together with perhaps unaltered residuals of 

 pyroxene, granules of iron ore, iron pyrites, quartz, and in seams 

 ■ and veins calcite and magnesian carbonates.^ 



Rocks, Rockweathering, and Soils, p. 101. 



